As noted in my above referenced patent application, the construction industry often desires to employ excavations of various types, such as foundations, trenches and the like. Where excavations are made in the earth, it is desirable to support the upright sidewalls of the excavation against collapse or to protect a sheltered workspace in the event of collapse. This is important not only from a cost standpoint, but also from the potential danger of injury or death to workers who are situated within the excavation. This is especially true in trenches which are excavated, for example, to lay conduit, pipe, communication lines and the like.
Various construction projects require that an elongated, narrow trench be excavated in the ground. By way of one example, where pipelines are being constructed, sections of pipe, for example, are laid in the bottom of the trench so that workers are required to descend into the trench to connect the pipe sections to each other or to otherwise install associated equipment. As sections of the pipeline are completed, the trench is filled-in behind the workers and more earth is excavated to extend the trench in front of the workers.
Naturally, should the sidewalls of a trench collapse, workers are exposed to great danger of bodily injury and even death. Therefore, it is desirable to protect against the collapse of the sidewalls of the trench, and some governmental agencies have even promulgated regulations directed to such structures, commonly referred to as "trench shields". Prior to the trench shield disclosed in my above referenced application, pre-existing trench shields had a relatively low strength-to-weight ratio. Thus, existing trench shields were unwieldly to insert and remove from the trench or to otherwise advance along the trench as worked progressed. The need to continually move a trench shield to provide a protected space for the workers also poses some danger of injury to the workers who may be struck by the trench shield during advancement or otherwise injured by the construction equipment necessarily employed to lift and to reposition the trench shield. Even with the improved strength-to-weight ratio of my trench shield disclosed in my above referenced application, repositioning of a trench shield can be cumbersome and time consuming. However in that application, I disclosed an auxiliary carriage assembly adapted to be employed with my trench shield. The present invention is thus directed to that carriage assembly as well as modifications thereto to be used with other types of trench shields as known in the art.